The present invention relates to block copolymer compositions capable of being processed by the application of pressure. The invention also provides methods for predicting phase diagrams of polymer blends and block copolymers.
A large number of manufactured articles are prepared from plastics. Generally, plastics are polymers that have relatively high viscosities. It has generally been accepted that to process polymers into a desired shape, a high temperature is required to reduce the viscosity and achieve a moldable state. A large drawback of today""s commercial plastics, however, is degradation that occurs when subjecting the polymers to high temperature. The degradation is heightened when such plastics are recycled, i.e. the plastic articles are again subjected to high temperatures during re-molding or re-forming. Thus, unlike metals such as steel and aluminum, the recycling of a polymer does not result in a material of equivalent grade, and the number of times these materials can be reused is limited to twice at the most. There are two principal reasons for this limitation. Firstly, the accidental mixing of chemically dissimilar plastics during recycling results in a dramatic loss in mechanical and optical quality. Secondly, each forming process the material encounters greatly alters its chemical structure, leading to dramatically reduced performance. The reasons for this are the high temperatures ( greater than 200xc2x0 C.) necessary for processing these materials.
Thus, there remains a need for materials that can be processed under conditions that do not promote degradation.
The present invention relates to the development of a new class of materials termed xe2x80x9cbaroplasticxe2x80x9d materials, based on polymer compositions that can be blends or block copolymers. The compositions disclosed herein can be processed primarily by applying pressure rather than temperature, thereby allowing them to be recycled multiply and with properties equivalent to the virgin material. A method is also disclosed for calculating phase diagrams for polymer blends and solutions that can be used as an aid in the design of new polymer materials or processes of manufacture for polymers.
One aspect of the present invention provides a method comprising the step of providing a polymeric composition comprising a soft component A having a Tg,s of less than room temperature and a hard component B in contact with the soft component A, the hard component having a Tg,h such that hard component has negligible flow at room temperature. The method further comprises the step of applying a pressure of at least about 100 psi such that the polymeric composition exhibits Newtonian flow at a temperature of less than 150xc2x0 C.
Another aspect of the present invention provides a polymeric composition comprising a soft component A having a Tg,s of less than room temperature, and a hard component B in contact with the soft component A, the hard component having a Tg,h such that hard component has negligible flow at room temperature. Components A and B are selected to have a relation xcfx86Axcfx86B[({tilde over (xcfx81)}A-{tilde over (xcfx81)}B)(xcex4A2xe2x88x92xcex4B2)] of the composition having a positive value at a temperature above 100xc2x0 C., wherein xcfx86A and xcfx86B represent volume fractions of the components A and B respectively, {tilde over (xcfx81)}A and {tilde over (xcfx81)}B represent reduced densities of the components A and B respectively, and xcex4A and xcex4B represent solubility parameters of the components A and B respectively. The densities xcfx81A and xcfx81B are matched as defined by the following relationship:
1.06xcfx81A less than xcfx81B less than 0.94xcfx81A.
Another aspect of the present invention provides a block copolymer comprising a soft block having a Tg,s of less than room temperature, and a hard block bonded to the soft block, the hard block having a Tg,h such that the hard block has negligible flow at room temperature. A pressure coefficient that favors miscibility, dTDOT/dP, of the block copolymer has an absolute value greater than about 30xc2x0 C./kbar.
Another aspect of the present invention provides a method for selecting a polymeric composition. The method comprises the steps of selecting a component A, having a polymerization index of NA, and selecting a component B, in contact with the component A, the component B having a polymerization index of NB. The method further comprises the steps of determining a value of a relation xcfx86Axcfx86B[({tilde over (xcfx81)}Axe2x88x92{tilde over (xcfx81)}B)(xcex4A2xe2x88x92xcex4B2)] of the composition such that the relation has a positive value at a temperature above 100xc2x0 C., wherein xcfx86A and xcfx86B represent volume fractions of the components A and B respectively, {tilde over (xcfx81)}A and {tilde over (xcfx81)}B represent reduced densities of the components A and B respectively, and xcex4A and xcex4B represent solubility parameters of the components A and B respectively. The densities xcfx81A and xcfx81B are matched as defined by the following relationship:
1.06xcfx81A less than xcfx81B less than 0.94 xcfx81A.
Another aspect of the present invention provides a method comprising the step of determining the phase diagram of a polymer composition by determining the free energy of the composition from the following equation:       Δ    ⁢          xe2x80x83        ⁢          g      mix        =            RT      ⁡              [                                                                              φ                  A                                ⁢                                                      ρ                    ~                                    A                                                                              N                  A                                ⁢                                  v                  A                                                      ⁢            ln            ⁢                          xe2x80x83                        ⁢                          φ              A                                +                                                                      φ                  B                                ⁢                                                      ρ                    ~                                    B                                                                              N                  B                                ⁢                                  v                  B                                                      ⁢            ln            ⁢                          xe2x80x83                        ⁢                          φ              B                                      ]              +                                        φ            A                    ⁢                      φ            B                    ⁢                                    ρ              ~                        A                    ⁢                                    ρ              ~                        B                          v            ⁢              (                  RT          ⁢                      xe2x80x83                    ⁢                      χ            FH                          )              +                  φ        A            ⁢                                    φ            B                    ⁡                      [                                          (                                                                            ρ                      ~                                        A                                    -                                                            ρ                      ~                                        B                                                  )                            ⁢                              (                                                      δ                    A                    2                                    -                                      δ                    B                    2                                                  )                                      ]                          .            
Other advantages, novel features, and objects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings, which are schematic and which are not intended to be drawn to scale. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention.